The present invention relates to a parachute opening shock emulator. More specifically, but without limitation, the present invention is an ejection seat simulator that simulates the parachute opening shock phase of an ejection.
Aviators and/or aircrew may have to eject from an aircraft, especially in combat situations, at high-speed and/or in adverse conditions. High speed ejection can be characterized by several phases. High-speed ejection phases include: initiation/catapult; under-seat rocket motor; drogue stabilization; parachute opening; and parachute landing. Each of these phases has inherent dangers and is capable of resulting in injury to the aircrew member. Typically, expensive component and system level testing is conducted on escape and man-mounted equipment systems to try to improve performance and to identify and mitigate safety risks to the aircrew member during high speed ejection. Under many ejection conditions, the most hazardous phase to the aircrew member is parachute opening shock. It is during this time that the aircrew member is rapidly separated from the relative protection of the aircraft and the aircraft seat. Currently, this event may only be examined during system level testing that is highly chaotic, difficult to obtain adequate data and video, and very costly. Due to the unpredictable nature of such testing, manikins have recorded large variations in measured accelerations and neck and head loads, even when attempting to regulate such variables. Currently, there is no system capable of reproducing the parachute opening shock phase repeatably in a controlled and cost effective manner.
With the expansion of the military aviator and aircrew population to include smaller males and females, an unknown level of risk has been introduced into high speed ejections. Additionally, helmets have changed to include night vision capabilities, head-up displays, and target acquisition devices. The effect of these systems increases head supported weight and shifts the center of gravity of the head region forward, a weaker condition for the neck physiologically. In order to quantitatively determine the overall effects on system performance and occupant safety, extensive system level testing is required.
During ejection, there is an abrupt deceleration of the body during line stretch and inflation of the aircrew's personal parachute. Peak acceleration during this phase is a function of aircrew mass properties, barometric and dynamic pressures, recovery parachute type, drag area and opening aids. Examples of opening aids include spreader guns and pull down vent lines, which decrease the time it takes to open a parachute and thus increase the resultant acceleration on the aircrew member. Lighter aircrew typically experience higher snatch forces and opening shocks due to their lesser mass. Depending on their initial position of the body, the linear and angular deceleration may be aggravated as the body is twisted and pulled into alignment with the parachute's opening vector. Additionally, currently used human tolerance limits for torso accelerations were derived specifically for the automotive industry. These tests were performed with subjects (such as humans and primates) in rigid seats with rigid head rests and specific restraint systems. This data has limited application to parachute opening shock in which the body is completely unrestrained and loading may be applied in any direction.
For the foregoing reasons, there is a need for a system capable of reproducing the parachute opening shock phase repeatedly, regardless of other conditions.